Superior quality graphene is highly sought in modern research due to the many desirable properties that it possesses. Graphene is a promising candidate for use in a wide variety of applications such as transparent flexible electrodes, photonic devices, energy storage, gas sensors and filters, transistors, coatings and solar energy and many more. Exceptional electrical, optical and mechanical properties of the material depend greatly on the quality of the synthesised graphene and the underlying substrate. Notably, the production of large area, single crystal graphene with a controlled number of layers has been an unyielding problem.
Chemical vapour deposition (CVD) has received much attention due to its simplicity, improved safety and low cost. However, in order to produce large area, single crystal graphene by CVD, the kinetics of the synthesis must be finely balanced. In most cases this is achieved only with low growth rates of up to 5 μm/min. The synthesis time is thus lengthy and significant quantities of source materials must be used. Moreover, when a solid substrate is used with CVD, graphene growth is strongly influenced by the crystallographic lattice of the substrate, as well as its defects, roughness and grain boundaries. A variety of methods are commonly used to attempt to artificially increase substrate grain size, eliminate grain boundaries and decrease the roughness of the surface. Examples of such methods include long annealing or reuse of the substrate, as well as mechanical, chemical and/or electrochemical polishing, and melting and re-solidification of the substrate. However, these methods are time and energy consuming, and thus costly. Alternatively, expensive single crystal substrates of limited size have been used, but such substrates cannot be upscaled.
There remains a need in the art for improved processes for the production of two-dimensional nanomaterials, in particular graphene.